Reactions Part One

UNMIX and MATCH!! COMPOUND The substance or substances initially involved in a chemical reaction. The outcome that a chemical change yields. A substance that participates either negatively or positively in a chemical reaction. A substance that prevents or decreases the rate of a chemical reaction MOCONPUD COPTURD TANTARCE BIOTHIRN PRODUCT REACTANT INHIBITOR A fixed ratio of two or more bonded elements that can be separated only by a chemical reaction. A blend of two or more substances that are together without being chemically combined and can usually be separated mechanically. MIXTURE TUXREIM TASTYCAL CATALYST

In chemistry, a reaction happens when two or more molecules interact and something happens. That's it. What molecules are they? How do they interact? What happens? Those are all the possibilities in reactions. The possibilities are nearly infinite. There are a few key points you should know about chemical reactions………. Recall A chemical change must occur. You start with one compound and turn it into another. That's an example of a chemical change. A steel garbage can rusting is a chemical reaction. That rusting happens because the iron (Fe) in the metal combines with oxygen (O2) in the atmosphere. When a refrigerator or air conditioner cools the air, there is no reaction. That change in temperature is a physical change. Nevertheless, a chemical reaction can happen inside of the air conditioner.

A reaction can involve pure atoms, ions, or molecules. Molecule – The smallest particle of a substance that retains all of the properties of the substance. It can be made of one atom up to many atoms. Ion - An atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. Oxygen Molecule Water Molecule Sugar Molecule Single reactions often happen as part of a larger series of reactions. Take something as simple as moving your arm. The contraction of that muscle requires sugars for energy. Those sugars need to be metabolized. You'll find that proteins need to move in a certain way to make the muscle contract. A whole series (hundreds actually) of different reactions are needed to make that simple movement happen.

A Brief History of Molecules…. READ ONLY A Brief History of Molecules…. The first molecules formed about 300,000 years after the Big Bang, or just under 15 billion years ago. They were the smallest kind of molecule - two hydrogen atoms joined together. As time went on, and supernovas from exploding stars shot out different kinds of atoms, different kinds of molecules formed and floated around in space. Because most of the atoms in space were hydrogen atoms, many of these molecules combined hydrogen with another kind of atom. So hydrogen combined with oxygen to make water molecules. Hydrogen combined with carbon to make hydrocarbons (what living things are built out of). Even before there were any planets, water and hydrocarbons were floating around in space on their own. Other molecules were made of heavier atoms, like silicon or gold. Still out in space, some hydrocarbons got together and formed bigger molecules called amino acids. When the planets did form, the ones that were further away from stars, like Jupiter and Neptune, were made mostly of lighter molecules like water and hydrocarbons. Earth, which formed about 4.5 billion years ago, was closer to the Sun, and made mostly of heavier molecules like iron. A lot of silicon and other minerals also got to Earth, where they make up the rocks of the Earth’s crust. We're not sure how or when the water, hydrocarbons, and amino acids got to Earth. But once they were on Earth, the amino acids got together to make more and more complicated molecules - maybe first ribonucleic, then proteins. The biggest organic molecule today is DNA Each molecule of DNA has more than two billion carbon atoms in it (plus a lot of other kinds of atoms too).

The rate of a reaction is the speed at which a reaction happens. Reactions happen, no matter what. Chemicals are always combining or breaking down. The rate of a reaction is the speed at which a reaction happens. Some reactions take hundreds, maybe even thousands of years while other can happen in less than one second. The rate of reaction depends mainly on the type of molecules that are combining but a few other factors as well. Why does increasing these factors result in a faster reaction? The collision theory says that the more collisions in a system, the more likely combinations of molecules will happen. If there are a higher number of collisions in a system, more combinations of molecules will occur. The reaction will go faster, and the rate of that reaction will be higher.

Exothermic – Heat or other energy flows from All chemical reactions involve a change in substances and a change in energy. Neither matter or energy is created or destroyed in a chemical reaction---only changed. Activation Energy - Energy that must be overcome in order for a chemical reaction to occur. The required energy can be lowered by a catalyst. Reaction Energy, on the other hand, is a result of the chemical reaction once it takes place. This energy can flow in either of two directions: Exothermic – Heat or other energy flows from the reaction to the surroundings. It is “released” Endothermic – Heat or other energy flows into the reaction from the surroundings. It is “absorbed”. What would each feel like if you touched it?